The crater Clavius in 2015

Since the weather outside these days does not allow for any kind of planetary astrophotography (or any type of astrophotography), I’m starting to reprocess some of the 2015 lunar images and also to process some of the previously untouched frames (around 500 Gb of data).

For now I won’t post all images since I don’t have enough time to process them, but one must be presented, since I’ve almost forgot about it and, after a second processing, it proved to be one of my best results in 2015.

The image was acquired on December 21th, using the homemade 355mm F/5 Newtonian at F/25 with the ASI 120MM-S and a Baader Red filter under perfect seeing conditions that lasted around 15 minutes. After this lunar area was acquired, the seeing dropped rapidly to around 6-7/10, and some time later to 5/10. Well, I can’t say I was very upset, since the seeing conditions at my location for this period of the year are usually very poor. Apparently I got very lucky…

The image now, showing crater Moretus (upper right) and Clavius, and also some mountains towards the South Pole.

Due to the very good conditions and resolution attained, I’ve pushed the original image size to 130%.

I’ve also wanted to compare this very good result with the previous ones from September and October, also under very good conditions. The result is presented below, in chronological order. The December 21th image easily strikes as the best from this series, followed by the very first one, from September 4th.

In the December 21th image, the smallest detectable craters are around 700 meters. I did get higher resolutions on the Moon in other previous sessions, but due to the position of Clavius on the Moon, the viewing angle does not allow for a good definition of smaller craters (they are viewed as highly elongated ellipses, so only the long axis is theoretically detectable, but that is not enough to solve these craters).

Perhaps this year I’ll get excellent seeing conditions again and get to higher focal lengths in order to have a better definition of the smallest craters.

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